Device for holding a tool

ABSTRACT

A device ( 1 ) for holding a tool ( 3 ), and the device ( 1 ) has a cavity ( 2 ) for the tool ( 3 ) and at least two channels ( 6 ) designed to allow the passage of a lubricant. Each channel has an inlet opening ( 7 ) and an outlet opening ( 8 ) for the lubricant. The at least two channels ( 6 ) are helically formed around the bore ( 2 ) and have a cross-section which increases in size from the inlet opening ( 7 ) to the outlet opening ( 8 ).

The invention relates to a device for receiving a tool in accordancewith the method defined in greater detail in the preamble of claim 1.

A generic device is known from DE 197 54 518 C2. In this instance, thereare formed in an inner wall of the device which is constructed as abushing a plurality of axially parallel grooves which extend through theentire length of the bashing and through which a lubricant is suppliedto a tool which is received in the bushing.

A thread cutting chuck which is constructed for minimum lubrication isdescribed in EP 0 956 919 A1.

A problem with the known solutions is in particular the separation whichoccurs during use of the aerosol which is used as a lubricant inside thechannels which extend through the device, in particular at higherspeeds, whereby a good lubricant supply to the tool which is arranged inthe device is not provided.

An object of the present invention is therefore to provide a devicewhich is for receiving a tool which is intended to be supplied with alubricant and with which using simple means a minimum lubrication of thetool is possible.

According to the invention, this object is achieved by the featuresmentioned in claim 1.

As a result of the channels which expand according to the invention fromthe respective inlet opening to the respective outlet opening and whichare used for the lubricant to flow through, a separation of thelubricant which is generally in the form of an aerosol is preventedsince the oil contained in the aerosol is retained in the aerosol asmist droplets as a result of the reduced pressure which is produced bythe expansion of the channel cross-section and the associated expansionof the gas contained in the aerosol, and cannot be deposited on thesurfaces of the channel.

As a result of the coiling according to the invention of the at leasttwo channels, the radial acceleration of the aerosol which flows throughthe channels during the rotation of the device is significantly reduced,which also contributes to preventing the separation of the aerosol.

According to the invention, there is consequently produced a devicewhich may be configured in such a manner that it can be used forstandard catalogue clamping chucks and standard catalogue tools and noadaptations are required when handling the tools. Furthermore, thedevice according to the invention can be configured in such a mannerthat it engages as round the tool so that no additional interferencecontour is provided by the device. Furthermore, as a result of thedevice according to the invention, very good concentricity can beachieved, whereby it can also be used at high speeds.

Another advantage of the solution according to the invention is that,with thin tools, an inner cooling channel can be dispensed with so thata higher tool stability, a lower level of wear and a higher quality areachieved. Furthermore, the solution according to the invention alsoresults in lower costs for the tool since a lubricant channel whichextends through the tool can be dispensed with.

If, in a very advantageous development of the invention, thecross-section of the outlet openings of the channels is from 8 to 15%greater than the cross-section of the inlet openings of the channels,this has particularly positive effects on the prevention of theseparation of the lubricant flowing through the channels.

A particularly simple embodiment of the cross-section increase of thechannels is produced, when the channels extend conically from the inletopening to the outlet opening.

Furthermore, there may be provision for the device to be produced bymeans of sintering, with particular regard to the production of thecoiled channels, sintering has been found to be a very simplepossibility for producing the device according to the invention.

A uniform lubricant supply to the tool contained in the device accordingto the invention is produced when there are provided two channels whichare offset through 180° with respect to each other.

This is also the case when alternatively there are provided threechannels which are offset through 120° with respect to each other. As aresult of the use of three channels, an even better lubricant supply tothe tool is achieved.

When the admixture is intended to be discharged from the channels in aparticularly fine distribution, there may further be provision for theoutlet openings of the channels to be constructed as Laval nozzles whichare orientated in the direction of the center axis of the device. As aresult of the use of such a Laval nozzle, splitting of the dropletswhich are contained in the aerosol is achieved, which leads to betterand more uniform wetting of the tool with the lubricant. In thisinstance, as a result of the outlet openings which are orientated in thedirection of the center axis of the device, there is produced acentering of the lubricant in the direction toward the tool.

In order to avoid to the greatest possible extent the separation of theaerosol as a result of the rotation of the device when it is used, therepay further be provision for the coiling of the channels to beconfigured in such a manner that an aerosol droplet which is containedin the lubricant moves at a predetermined speed as a superimposedmovement comprising rotation and inherent speed in an at leastsubstantially linear manner from the inlet opening to the outletopening.

A particularly advantageous use of the device according to the inventionis produced when it is constructed as a tool receiving bushing forarrangement inside a clamping chuck.

In this context, another advantageous embodiment of the invention mayinvolve the sum of the cross-sectional surface-areas of the channels inthe region of the inlet openings at least, substantially correspondingto the cross-section of an outlet opening of a channel which is providedfor the lubricant to flow through in the clamping chuck. In this manner,the pressure and the flow speed within the entire channel through whichthe lubricant flows are kept constant both inside the clamping chuck andinside the tool receiving bushing which is received in the clampingchuck.

An embodiment of the invention is illustrated schematically below withreference to the drawings.

In the drawings:

FIG. 1 is a cross-sect ion through a device according to the inventionwhich in this embodiment is constructed as a tool receiving bushingwhich is received in a clamping chuck;

FIG. 2 is a perspective illustration of the device according to theinvention from FIG. 1 with the channels which are contained therein andwhich are provided for a lubricant to flow through;

FIG. 3 is an enlarged illustration in accordance with line III from FIG.2; and

FIG. 4 shows the cross-sectional, surface-areas of the inlet openings ofthe channels inside the device which is constructed as a tool receivingbushing and an outlet opening of the channel inside the clamping chuck.

FIG. 1 shows a device 1 which is constructed in the embodimentillustrated as a tool receiving bushing 1 a and which has a central hole2 for receiving a tool 3, for example, a milling or drilling tool. Thetool receiving bushing 1 a itself is received in a clamping chuck 4which can be clamped in a manner known per se in a machine tool which isnot illustrated. The connection of the tool receiving bushing 1 a to theclamping chuck 4 and the connection of the tool 3 to the tool receivingbushing 1 a can also be carried, out in a manner known per se, forexample, by means of shrink connections. In addition to shrinking, otherconnection possibilities are naturally also conceivable.

There extends in the clamping chuck 4 a central channel 5 which isprovided for a lubricant which is not illustrated to flow through. Inthis instance, the channel 5 serves to supply the lubricant to at leasttwo channels 6 which are located inside the tool receiving bushing 1 aand through which the lubricant also flows in order to supply toelubricant to the tool 3. There is preferably used as a lubricant anaerosol in which oil droplets are preferably dissolved in a gas, suchas, for example, air or compressed air.

In an embodiment which is not illustrated, it would also be possible forthe channels 6 to be provided in the clamping chuck 4, that is to say,for the tool receiving bushing 1 a to be omitted and the device 1 to beformed by the clamping chuck 4 in which the tool 3 is then directlyreceived.

FIG. 2 is a perspective illustration of the tool receiving bushing 1 aand the path of the (in this instance) three channels 6 through it canbe seen. This shows that the in this instance) three channels 6 extendin a helical manner around the hole 2 of the tool receiving bushing 1 a.In the present case, the three channels 6 are arranged offset through120° with respect to each other in order to achieve a symmetry thereof.In an embodiment which is not illustrated and in which only two channels6 are provided, these could accordingly be arranged offset through 180°with respect to each other. The same also applies to a larger number ofchannels 6 inside the tool receiving bushing 1 a. The number of channels6 may, for example, be dependent on the size of the tool 3 which isreceived in the hole 2. Thus, a variant with four or more channels 6 isalso conceivable in order to also enable devices 1 with a minimumdiameter, in particular when they are constructed as a tool receivingbushing 1 a.

FIG. 2 is further a developed view of one of the channels 6 from whichit can be seen that the channels 6 have a cross-section which increasesfrom an inlet opening 7 at the upper side of the tool receiving bushing1 a to an outlet opening 8 at the lower side of the tool receivingbushing 1 a. This increasing cross-section of the channels 6 serves toprevent the separation of the lubricant which flows through the channels6. In the embodiment which is illustrated in FIG. 2, the channels 6extend conically from the inlet opening 7 to the outlet opening 8.Furthermore, in the present embodiment, the cross-sect ion of the outletopenings 8 of the channels 6 is from 8% to 15% greater than thecross-section of the inlet openings 7 of the channels 6. However, therelationship of the cross-section of the outlet openings 6 to thecross-section of the inlet openings 7 is not illustrated to scale inFIG. 2.

The channel routing of she channels 6 is configured for a minimumlubrication of the tool 3 and preferably does not have any sharp-edgedcorners in order to prevent formation of droplets and consequently aseparation. Instead, all the sharp edges, such as, for example, 90°corners, are rounded at transition locations, such as, for example, atthe inlet openings 7, or inside the channels 6 so as to promote flow.

The coiling of the channels 6 is in this instance configured in such amanner that an aerosol droplet which is contained in the lubricant movesat a predetermined speed as a superimposed movement comprising rotationand inherent speed at least substantially in a linear manner from theinlet opening 7 to the outlet opening 8. If, for example, a millingspindle is configured for a speed of 20,000 rpm, the length of the toolreceiving bushing 1 a is 0.08 m and the flow speed of the aerosol is 10m/s, an oil droplet flows through the tool receiving bushing 1 a in atime of 0.008 s. Within this time of 0.008 s, the spindle andconsequently also the tool receiving bushing 1 a have traveled 2.66revolutions so that the coiling of the channels is configured for 2.66transitions over the length of the tool receiving bushing 1 a of 0.08 m.That is to say, therefore, in this instance, a channel 6 turns 2.66times or at an angle of approximately 960° about the hole 2 of the toolreceiving bushing 1 a. As a result of such a configuration of thechannels 6, no transverse acceleration acts in principle on the oildroplets contained in the aerosol.

The enlarged illustration of FIG. 3 illustrates one of the outletopenings 8 of one of the channels 6. From this it can be seen that theoutlet opening 8 is constructed in the form of a Laval nozzle in orderto split the oil droplets located in the aerosol. Furthermore, it can beseen that the outlet opening 8 is orientated in the direction of acenter axis 9 of the tool receiving bushing 1 a.

FIG. 4 shows the cross-sectional surface-areas of the inlet openings 7of the channels 6 which extend through the tool receiving bushing 1 aand the cross-sectional surface-area of an outlet opening 10 of thechannel 5 which extends through the clamping chuck 4. Preferably, thetotal of the cross-sectional surface-areas of the channels 6 in theregion of the inlet openings 7 is at least substantially equal to thecross-sectional surface-area of the outlet opening 10 of the channel 5in the clamping chuck 4 so that a constant pressure and a constant flowspeed is achieved within the entire channel through which the lubricantflows inside the clamping chuck 4 and the tool receiving bushing 1 a.

In principle, the tool receiving bushing 1 a may be constructed inextremely different lengths and diameters, both with regard to the outerdiameter thereof and with respect to the diameter of the hole 2.Preferably, the tool receiving bushing 1 a or generally the device 1 isproduced by means of sintering from a suitable material.

The invention claimed is:
 1. A device (1) for receiving a tool (3), thedevice (1) having a recess (2) for the tool (3) and having at least twochannels (6) which are provided for a lubricant to flow through andwhich each have an inlet opening (7) and an outlet opening (8) for thelubricant, wherein the at least two channels (6) have a cross-sectionalarea which increases from the inlet opening (7) to the outlet opening(8) and the at least two channels (6) extend around the hole (2) in ahelical manner.
 2. The device (1) according to claim 1, wherein across-sectional area of the outlet openings (8) of the channels (6) isbetween 8 to 15% greater than a cross-sectional area of the inletopenings (7) of the channels (6).
 3. The device (1) according to claim1, wherein the at least two channels (6) each extend conically from theinlet opening (7) to the outlet opening (8).
 4. The device (1) accordingto claim 1, wherein the device (1) is produced by sintering.
 5. Thedevice (1) according to claim 1, wherein the at least two channels (6)are offset by 180° with respect to one another.
 6. The device (1)according to claim 1, wherein the at least two channels (6) comprisefirst, second and third channels (6) which are offset by 120° withrespect to one another.
 7. The device (1) according to claim 1, whereinthe outlet openings (8) of the at least two channels (6) are constructedas Laval nozzles which are orientated in a direction of a center axis(9) of the device (1).
 8. The device (1) according to claim 1, whereincoiling of the at least two channels (6) is configured in such a mannerthat an aerosol droplet, which is contained in the lubricant, moves at apredetermined speed as a superimposed movement comprising rotation andinherent speed in an at least substantially linear manner from the inletopening (7) to the outlet opening (8).
 9. The device (1) according toclaim 1, the device (1) is constructed as a tool receiving bushing (1 a)for arrangement inside a clamping chuck (4).
 10. The device (1)according to claim 9, wherein a sum of cross-sectional surface-areas ofthe at least two channels (6), in a region of the inlet openings (7), atleast substantially corresponds to a cross-section of an outlet opening(10) of a channel (5) which is provided for the lubricant to flowthrough in the clamping chuck (4).
 11. A device for receiving a tool,the device comprising: a recess for receiving the tool, the recessextending along a longitudinal axis of the device; at least twochannels, each of the at least two channels having an inlet opening andan outlet opening, and the at least two channels extending axially alongthe device and facilitating flows of lubricant through the device fromthe inlet openings to the outlet openings; each of the at least twochannels having a lateral cross-section, the cross-section of each ofthe at least two channels having an area that increases from the inletopening to the outlet opening; and the at least two channels extendaround the hole in a helical manner.